Recycled material mixing machine

ABSTRACT

A machine for combining powder material with cohesive site-won spoil has an input hopper ( 4 ) which provides a preliminary breaking up step. Some lime is added from a lime feeder ( 6 ) as the material is transported to a pan mixer ( 8 ). During transport a rotavator ( 30 ) acts on the cohesive material so that finely divided material enters the mixing means ( 8 ). Further powder ingredients can be added to the components in the pan mixer ( 8 ) by means of a powder ingredient supply system ( 10 ).

BACKGROUND OF THE INVENTION

[0001] The present invention relates to apparatus for combining thecomponents of a material in building and civil engineering operationsand particularly for material for use as backfill in roadwork trenchexcavation.

[0002] A process of recycling site-won spoil to provide a materialsuitable for use as a backfill is described in international patentapplication PCT GB01/03083 filed on 9 Jul 2001 by the present applicant.The manufacture of such a material requires the mixing of apredominantly non-granular cohesive material such as a clay soil withpowder components in specific proportions. These powder components maybe lime, cement and/or pulverised fly ash (PFA) also known as pulverisedfuel ash.

TECHNICAL PROBLEM

[0003] Technical problems arise in ensuring a good distribution of thepowder components within the cohesive material and also in producing amaterial which has consistently proportioned ingredients.

[0004] The earlier application, which was unpublished at the prioritydate of this application, proposed a machine in which a mixing screw isused to amalgamate the components. Whilst satisfactory, it is possiblefor such screws to become clogged when used with cohesive materials suchas heavy clay and therefore the present invention proposes analternative approach in which the cohesive components are broken upprior to the addition of the powder ingredients. Preferably mixing isthen carried out by vanes operating within a pan mixer, which is lessliable to clogging. Preferably some of the lime is also added at anintermediate stage while the spoil is being broken up.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] In order that the invention may be well understood an embodimentthereof will now be described, by way of example only, with reference tothe accompanying diagrammatic drawings, in which:

[0006]FIG. 1 is a diagrammatic sectional view of a machine; and

[0007]FIG. 2 is a top plan view of the machine of FIG. 1.

[0008] The machine is assembled on a platform 2 so that it can betransported. The principle elements of the machine are an input hopper 4shown on the right hand side of FIG. 1, a lime feeder 6, a pan mixer 8and a powder ingredient supply system 10.

[0009] The object of the machine is to deliver to the pan mixer 8 powderingredients from the supply system 10 and clay spoil which has beenbroken up and pre-mixed with lime. The control of the proportions of thematerial is made possible by this arrangement.

[0010] The cohesive and any granular material input 4 is via a rotarysizer machine which contains inclined blades which break up the cohesivematerial as it passes through onto a conveyer 20 located beneath therotary sizer hopper 4.

[0011] The cohesive material may be spoil from a trench excavation inputdirectly during construction. Depending on ground conditions this may bevery lumpy and the degree of water content may vary. These factors maybe measured in order to determine the required proportions of powderingredients to be added. As well as site-won spoil additional granularmaterials could be added through the hopper 4. The function of the inputhopper is to provide a preliminary breaking up step so that the materialfed to the conveyer 20 is divided up so that it provides a significantsurface area to be exposed to the lime.

[0012] The belt conveyer 20 incorporates a belt weigher, which allowsthe monitoring of the quantity of the cohesive material being suppliedin order to maintain the correct proportions. The belt conveyer 20delivers its load onto an upwardly inclined conveyer track 22. Theconveyer track 22 has a conveying surface defined by spaced bars 24through which sufficiently finely divided material can pass fallingthrough this slotted conveyer 22 onto a lower conveyer belt 26.

[0013] The lime feeder 6 is a hopper positioned at the junction of theconveyer 20 and the inclined slotted conveyer 22. The lime feeder 6contains a rotary valve 28 so as to provide a controlled feedmaintaining the desired proportion of lime to the weight of cohesivematerial being delivered. Further lime may also be added later.

[0014] A rotavator 30 is mounted above the slotted conveyer 22 in orderto be able to act on the remaining large elements of cohesive materialbeing conveyed upwards. Because the larger lumps will tend to fallbackwards along the conveyer, those reaching the upper end where theyare tipped into the pan mixer 8 will be of relatively modest size, whichwill facilitate the final mixing process with other powder ingredients.

[0015] The rotavator 30 is adapted to be movable upwardly and downwardlyrelative to the surface of the slotted conveyer 22. Moving the rotavator30 down will allow it to act on smaller sized lumps. The rotavator 30may also need to be lifted away for cleaning purposes. The rotavator 30is provided with a shield 32 so that all material on which it acts isdirected downwardly back onto the slotted conveyer 22.

[0016] The rotavator 30 extends across the width of the slotted conveyer22.

[0017] Belt scrapers 40 are provided on the undersides of the conveyers20 and 26 to clean the belts and to prevent material being retained onthe belt surfaces on the undersides of these conveyers. These scrapersare positioned so that any remaining material is either deposited ontothe slotted conveyer from conveyer 20 or into the pan mixer 8 from theconveyer 26.

[0018] The powder ingredients dispenser 10 comprises two compartments50, 52 for different powder ingredients such as lime and fly ash and/orcement. A two compartment arrangement is shown. Each compartment 50, 52has its own auger feeder 54 which can be arranged to supply a controlledrate of feed of the powder into the pan mixer 8.

[0019] The pan mixer 8 has a rotary blade or vane arrangement which isdriven by means of a motor. An outlet 60 from the pan mixer 8 is adaptedto deposit the thoroughly mixed material onto a conveyer 62 through anopening in the platform 2.

1. A machine for recycling site-won spoil comprising predominantlynon-granular cohesive material from an excavation for immediate re-useas a backfill, comprising means (4) for receiving excavated cohesivematerial, means (6, 10) for adding a measured amount of powder material,mixing means (8) for thoroughly mixing the components and dischargingthem from the machine, and means (4, 22, 30, 26) for breaking up thecohesive material before it enters the mixing means (8).
 2. A machine asclaimed in claim 1, wherein the mixing means comprises a pan mixer (8)having a rotary blade or vane.
 3. A machine as claimed in claim 1 or 2,wherein the means for adding a measured amount of powder materialcomprises means (6) for feeding lime onto the excavated cohesivematerial at an intermediate stage while the spoil is being broken up.